2. Field of the Invention
This invention relates to novel compositions and the novel methods of their use for neutralization and clean-up of hazardous acidic spills.
2. Prior Art
Various compositions have been known in the past to be useful for the clean-up of hazardous organic waste materials. Some prior art references describe methods for neutralizing acid spills. Several references describe compositions for neutralizing and solidifying liquid wastes, particularly raw sewage. However, these prior art compositions and methods for acid waste neutralization entail certain disadvantages.
U.S. Pat. No. 3,994,821 (Seidenberger) relates to the control and clean-up of a mineral acid spill using a granular composition containing 36.5 to 47.5% by weight ground marble chips, about 35 to 45.5% by weight granular soda, about 16.5 to 21.5% by weight granular magnesia and about 0.008 to 0.012% by weight of an appropriate normally solid pH indicator. Ground marble chips are composed of calcium carbonate. The granular spill control composition of this patent is employed to control and clean-up substantially all of a spilled mineral acid by applying the granular composition to this spill surface from the perimeter of the spill inward in a quantity sufficient to absorb all the spilled acid. Although the spill is generally neutralized by this granular composition, the acids having a high heat of neutralization may not be completely neutralized, thus continuing to pose a threat. Further, the method of applying this composition necessitates workers' exposure to the spill.
U.S. Pat. No. 4,210,460 (Seidenberger) relates to a composition for controlling and clean-up of a spill of hydrofluoric acid. The composition may be in one of two forms: an aqueous solution and a powdered composition. The aqueous solution is composed of about 20 to 29% by weight of calcium acetate and about 71-65% by weight of water. The powdered composition is composed of about 99.90 to 99.99% by weight powdered magnesia and about 0.01 to 0.1% by weight of an appropriate normally solid pH indicator. The powdered magnesium oxide composition can be sprinkled onto the hydrofluoric acid spill. The pH indicator will indicate by color change when an essentially safe pH condition has been reached. This composition also has the disadvantages of less-than total neutralization and the risk of exposure to the spill.
U.S. Pat. No. 4,207,116 (Been et al.) described a granulated absorbent material composed of cement, an inorganic water-absorbing swelling agent, sand or ground stone, water and, optionally, dye stuffs and other additives. The composition is mixed to form a paste, the paste is allowed to harden and the hardened material dried and granulated. The cement hardens with the water and acts as a skeleton-forming substance which provides the granulated material with hardness. The sand or ground stone acts as an inert blending agent to lower the cost price of the granulated material. The water-absorbing swelling agent, which can be a clay, aids in absorbing liquids such as water, oil and for absorbing smells. All types of clays may be used as inorganic swelling agents such as sepiolite, montmorillonite, kaolins, diatomaceous earth and bentonite. This composition is contemplated for use in cat litter, rather than in containing, neutralizing and solidifying hazardous acid spills.
U.S. Pat. No. 3,980,558 (Thompson) relates to a method for disposing of liquid or semi-liquid waste containing soluble toxic materials containing the waste and a solidifying agent which consists of a hydraulic cement which will set upon standing to a contiguous rock-like solid consistency. This prevents the waste from leaching. The term "hydraulic cement" refers to all mixtures of lime, silica, and alumina, or of lime and magnesia, silica, alumina and iron oxide and other like mixtures of ingredients. A particularly preferred mixture is Type I Portland Cement. The patent states that the process of this invention is particularly useful in disposing of aqueous sludge waste from chemical processes for the manufacture of phosphoric acids, particularly aqueous filter and sludges, which normally contain high levels of arsenic and dissolved arsenic compounds, as well as hydrogen sulfide and other sulphur compounds. Although this composition contains and solidifies waste, it is not essentially a neutralizing composition. Further, it requires solidification by mixing with the waste materials. This is impractical where there has been a spill, which does not lend itself to mixing.
U.S. Pat. No. 4,518,508 (Conner) describes a method for treating aqueous liquid and semi-liquid wastes by solidification. The method of the invention described requires that a dry water-reactive solidification agent comprising cement, a dry water absorbent material and a powdered alkali metal silicate, sufficient to convert the mixture into a consolidated chemically and physically stable solid product, are added to aqueous liquid or semi-liquid waste. The waste can then be solidified and set, forming a synthetic rock-like material. This composition acts to neutralize the acidity of the waste in part. However, it may not render complete neutralization. Another disadvantage is that it must be mixed with the waste.
U.S. Pat. No. 4,547,290 (Pichat) describes a process for solidifying strongly acid or alkaline liquid waste. According to this patent, clays can be used directly in a very acidic or strongly alkaline aqueous waste to make it possible to transform this waste into stable solid materials. According to the invention, a clay material is dispersed in the waste by stirring, and the waste neutralized. A hydraulic and/or calcium binder addition then follows. All types of fresh or dried clays can be used, such as pure clays, mixtures including attapulgites and metal carbonates. During the neutralization process lime, ground limestone, calcium carbonate base wastes, calcium silicate and/or aluminates may be added, particularly to acidic wastes. The third stage of the process causes the material to be capable of solidification. Materials such as Portland cement may be added to the pasty mass that has been formed. Again, this composition must be mixed to form a slurry in order to neutralize and solidify the waste, necessitating close contact with the waste. This method is therefore impractical when applied to acid spills.
U.S. Pat. No 3,837,872 (Conner) describes an aqueous solution of an alkaline metal silicate mixed with waste material and a silicate setting agent which causes the silicate and waste material to react with each other. This invention relates particularly to the treatment of raw human waste. According to the invention, wastes are mixed with an alkaline metal silicate such as sodium silicate which, in the presence of a silicate setting agent, causes the mixture to undergo consolidation and solidification. The setting agents include acids or acidic materials which cause gelation of the silicate. Setting agents include Portland cement, lime, gypsum and calcium carbonate and aluminum, iron, magnesium, nickel, chromium, manganese or copper compounds. This method also has the disadvantage of requiring close contact with wastes for solidification as well as actual mixing. This method cannot be used for spill control.
U.S. Pat. No. 4,297,304 (Scheffler et al.) describes a method for solidifying high and medium radioactivity and/or actinide-containing aqueous waste concentrates for fine-grained solid wastes suspended in water for final noncontaminating storage. The waste concentrates or suspensions are set by evaporation to form an evaporate having a water content in the range between 40 and 80 percent by weight and a solid content with a metal iron and/or metal oxide component between 10 and 30 percent by weight of the evaporate. The clay-like substances include silica, alumina and portland cement. The metal oxides can include MgO. The pH of the evaporate is then set to between 5 and 10, and kneaded with a clay-like substance containing a small quantity of cement or a mixture of clay-like substance with a small quantity of cement containing an additive for suppressing the volatility of alkalis. Molded bodies are produced from the kneaded mass, heat treated, calcined and fired. The bodies are then enclosed on all sides in a dense, continuous ceramic or metallic matrix. This method is not advantageous for use with acid spills: the composition must be mixed with the waste for solidification.
Thus, prior art methods have several disadvantages when applied to hazardous acidic spills. A composition which can neutralize several types of acids, which can be applied from a safe distance without danger to the workers is not suggested in the prior art.